Genetic marker clue to the progression of Alzheimer's disease

A genetic marker indicating high levels of a protein called tau in patients was found to be associated with rapid progression of the condition.

Researchers studied 846 patients with elevated levels of tau in their cerebrospinal fluid (CSF) – a clear fluid found in the brain – after recent studies showed that the presence of a particular form of the protein in the CSF is an indicator of the disease.

They also looked at single DNA variations in the patients and identified the genetic marker linked to elevated tau levels.

The finding, combined with the ability to measure tau in the CSF, may mean that if drugs could inhibit the protein's accumulation in the fluid, prevention or delay of some of the devastation associated with Alzheimer's might be possible, the scientists said.

The study, carried out by an international team of experts led by Washington University School of Medicine in St Louis, Missouri, in the US, is published in the journal Public Library of Science Genetics.

Senior investigator Alison M Goate said: "People who carry this genetic marker tend to have higher tau levels at any given stage of the disease than individuals without it.

"Until now, most studies of genetic risks associated with Alzheimer's disease have looked at the risk of developing the disease, not the speed at which you will progress once you have it. The genetic marker we've identified deals with progression."

For many patients and their families, this information may be more useful than the knowledge that a person may be developing Alzheimer's damage in the brain even if that individual has not yet developed clinical symptoms, Goate added.

Dr Carlos Cruchaga, assistant professor of psychiatry at Washington University and first author of the study, said: "We have looked at data from three separate, international studies, and in all three we found the same association.

"So we are confident that it is real and that this gene variant is associated with progression in Alzheimer's disease."